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From: Edward Cree <ecree@solarflare.com>
To: Lorenz Bauer <lmb@cloudflare.com>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
	"Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Song Liu" <songliubraving@fb.com>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Martin Lau" <kafai@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"Marek Majkowski" <marek@cloudflare.com>,
	"David Miller" <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	kernel-team <kernel-team@cloudflare.com>
Subject: Re: [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls
Date: Mon, 7 Oct 2019 20:21:22 +0100	[thread overview]
Message-ID: <4124d5a6-06b7-ad03-f5fe-4b61e55fff27@solarflare.com> (raw)
In-Reply-To: <CACAyw98mYK3Psv61+BDcyk56PbnJf2JhdfDLsB0eD4vLJJnGYQ@mail.gmail.com>

On 07/10/2019 18:12, Lorenz Bauer wrote:
> Sure, but this is the simplest, not necessarily realistic use case. There
> is a reason that libbpf has the API it has. For example, we patch our
> eBPF before loading it. I'm sure there are other complications, which is
> why I prefer to keep loading my own programs.
Any reason why you can't have the client patch the eBPF (possibly with
 libbpf) before supplying the patched object file to the loaderiser?

>> No, I'm talking about doing a linker step (using the 'full-blown calls'
>>  _within_ an eBPF program that Alexei added a few months back) before the
>>  program is submitted to the kernel.  So the BPF_CALL|BPF_PSEUDO_CALL insn
>>  gets JITed to a direct call.
> Ah, I see. I'm not sure whether this restriction has been lifted, but those
> calls are incompatible with tail calls. So we wouldn't be able to use this.
Indeed, tail calls don't fit into my scheme, because being a tail-call from
 the subprogram doesn't make you a tail-call from the dispatcher program.
But AIUI tail calls are only in use today in various work-arounds for the
 lack of proper linking (including dynamic linking).  If we supported that,
 would you still need them?

>> OK, but in that case xdpd isn't evidence that the "loader" approach doesn't
>>  work, so I still think it should be tried before we go to the lengths of
>>  pushing something into the kernel (that we then have to maintain forever).
> Maybe this came across the wrong way, I never said it is.
No, you didn't (sorry).  Toke somewhat implied it, which is what I was
 responding to there.

-Ed

  reply	other threads:[~2019-10-07 19:21 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 13:30 [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through chain calls Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 1/9] hashtab: Add new bpf_map_fd_put_value op Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 2/9] xdp: Add new xdp_chain_map type for specifying XDP call sequences Toke Høiland-Jørgensen
2019-10-02 15:50   ` Lorenz Bauer
2019-10-02 18:25     ` Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 3/9] xdp: Support setting and getting device chain map Toke Høiland-Jørgensen
2019-10-02 15:50   ` Lorenz Bauer
2019-10-02 18:32     ` Toke Høiland-Jørgensen
2019-10-02 18:07   ` kbuild test robot
2019-10-02 18:29   ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 4/9] xdp: Implement chain call logic to support multiple programs on one interface Toke Høiland-Jørgensen
2019-10-02 17:33   ` kbuild test robot
2019-10-02 17:53   ` kbuild test robot
2019-10-02 13:30 ` [PATCH bpf-next 5/9] tools/include/uapi: Add XDP chain map definitions Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 6/9] tools/libbpf_probes: Add support for xdp_chain map type Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 7/9] bpftool: Add definitions " Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 8/9] libbpf: Add support for setting and getting XDP chain maps Toke Høiland-Jørgensen
2019-10-02 13:30 ` [PATCH bpf-next 9/9] selftests: Add tests for XDP chain calls Toke Høiland-Jørgensen
2019-10-02 15:10 ` [PATCH bpf-next 0/9] xdp: Support multiple programs on a single interface through " Alan Maguire
2019-10-02 15:33   ` Toke Høiland-Jørgensen
2019-10-02 16:34     ` John Fastabend
2019-10-02 18:33       ` Toke Høiland-Jørgensen
2019-10-02 20:34         ` John Fastabend
2019-10-03  7:48           ` Toke Høiland-Jørgensen
2019-10-03 10:09             ` Jesper Dangaard Brouer
2019-10-03 19:45               ` John Fastabend
2019-10-02 16:35 ` Lorenz Bauer
2019-10-02 18:54   ` Toke Høiland-Jørgensen
2019-10-02 16:43 ` John Fastabend
2019-10-02 19:09   ` Toke Høiland-Jørgensen
2019-10-02 19:15   ` Daniel Borkmann
2019-10-02 19:29     ` Toke Høiland-Jørgensen
2019-10-02 19:46     ` Alexei Starovoitov
2019-10-03  7:58       ` Toke Høiland-Jørgensen
2019-10-02 18:38 ` Song Liu
2019-10-02 18:54   ` Song Liu
2019-10-02 19:25     ` Toke Høiland-Jørgensen
2019-10-03  8:53       ` Jesper Dangaard Brouer
2019-10-03 14:03         ` Alexei Starovoitov
2019-10-03 14:33           ` Toke Høiland-Jørgensen
2019-10-03 14:53             ` Edward Cree
2019-10-03 18:49               ` Jesper Dangaard Brouer
2019-10-03 19:35               ` John Fastabend
2019-10-04  8:09                 ` Toke Høiland-Jørgensen
2019-10-04 10:34                   ` Edward Cree
2019-10-04 15:58                     ` Lorenz Bauer
2019-10-07 16:43                       ` Edward Cree
2019-10-07 17:12                         ` Lorenz Bauer
2019-10-07 19:21                           ` Edward Cree [this message]
2019-10-07 21:01                         ` Alexei Starovoitov
2019-10-02 19:23   ` Toke Høiland-Jørgensen
2019-10-02 19:49     ` Song Liu
2019-10-03  7:59       ` Toke Høiland-Jørgensen

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